As well known, oil-immersed solenoids are widely used in valve devices for controlling hydraulic equipment for construction machinery and industrial machinery. A generally-known oil-immersed solenoid includes a coil, a fixed magnetic pole, and an armature, and energizes the coil in the state where hydraulic oil is filled in a space that houses the armature, thereby causing the fixed magnetic pole to suck the armature so as to move a shaft fixed to the armature.
For example, Patent Document 1 discloses such an oil-immersed solenoid. As shown in FIG. 15, the solenoid 100 includes a casing 115 forged by integrating a base 111, an outer cylinder 112, a lower fixed magnetic pole 113 and a flange 114, an inner cylinder 120 jointed to the lower fixed magnetic pole 113 of the casing 115, a plunger 130 having an armature 131 housed in the inner cylinder 120, a bobbin 142 around which a coil 141 is wound, and a cover 150, and energizes the coil 141 to move the plunger 130.
Patent Document 1: JP 2006-300222 A
However, in the solenoid 100 described in Patent Document 1, as shown in FIG. 15, the inner cylinder 120 is formed by brazing an upper fixed magnetic pole 121 as a magnetic body to a cylinder 122 as a nonmagnetic body, and the inner cylinder 120 is brazed to the lower fixed magnetic pole 113 of the casing 115.
Then, the plunger 130 is inserted into the inner cylinder 120 jointed to the casing 115, the bobbin 142 around which the coil 141 is wound is fitted to the outer circumference of the inner cylinder 120, the cover 150 is placed thereon and then, a front end of the outer cylinder 112 is swaged to the cover 150 to assemble the solenoid 100.
In the solenoid 100 thus assembled, the inner cylinder 120 is formed by brazing and the inner cylinder 120 is brazed to the lower magnetic pole 113 of the casing 115. Since multiple times of brazing is required, the number of man-hours needed for assembling is large, disadvantageously increasing assembling costs.
Therefore, an object of the present invention is to provide an oil-immersed solenoid that can be easily assembled, greatly reducing the number of man-hours needed for assembling, and in turn, decreasing assembly costs.